Thermal interface material structures including protruding surface features to reduce thermal interface material migration

ABSTRACT

Forming a thermal interface material structure includes forming an assembly that includes a thermal interface material disposed between a first mating surface and a second mating surface. The first mating surface is associated with a module lid, and the second mating surface is associated with a heat sink. Protruding surface features are incorporated onto the first mating surface or the second mating surface. The process also includes compressing the assembly to form a thermal interface material structure. The thermal interface material structure includes the thermal interface material disposed within an interface defined by the first mating surface and the second mating surface. The protruding surface features protrude from the first mating surface or the second mating surface into selected areas of the interface to limit relative movement of the mating surfaces into the selected areas during thermal cycling to reduce thermal interface material migration out of the interface.

BACKGROUND

In an electronic device, a thermal interface material (also referred toas a “TIM”) is a material (e.g., a grease or a putty) that is disposedbetween a heat generating component of an electronic device (e.g., adie, a memory component, an inductor, etc.) and a heat dissipatingcomponent (e.g., a heat spreader or a heat sink) in order to facilitateefficient heat transfer between the heat generating component and theheat dissipating component. The powering up or powering down of theelectronic device may cause temperature changes which may cause arelative motion between the heat generating component and the heatdissipating component, including in-plane motion and out-of-plane motiondue to coefficient of thermal expansion (CTE) mismatch. This relativemotion may cause the thermal interface material to squeeze out of theinterface gap. This phenomenon is commonly referred to as “pump-out” ofthe thermal interface material and results in increased thermalresistance due to loss of material from the interface.

SUMMARY

According to an embodiment, a process of forming a thermal interfacematerial structure is disclosed. The process includes forming anassembly that includes a thermal interface material disposed between afirst mating surface and a second mating surface. The first matingsurface is associated with a module lid, and the second mating surfaceis associated with a heat sink. Protruding surface features areincorporated onto the first mating surface or the second mating surface.The process also includes compressing the assembly to form a thermalinterface material structure. The thermal interface material structureincludes the thermal interface material disposed within an interfacedefined by the first mating surface and the second mating surface. Theprotruding surface features protrude away from the first mating surfaceor the second mating surface into selected areas of the interface tolimit relative movement of the first mating surface and the secondmating surface into the selected areas during thermal cycling to reducethermal interface material migration out of the interface.

According to another embodiment, an electronic component coolingassembly is disclosed that includes an electronic component, a modulelid, a heat sink, and a thermal interface material. The module lid formsa heat spreader surrounding the electronic component, and the module lidhas surface features protruding away from a module lid mating surface.The heat sink has a heat sink mating surface, and the thermal interfacematerial is disposed within an interface between the module lid matingsurface and the heat sink mating surface. The surface features protrudeaway from the module lid mating surface into selected areas of theinterface to limit relative movement of the mating surfaces into theselected areas during thermal cycling in order to reduce migration ofthe thermal interface material out of the interface.

According to another embodiment, an electronic component coolingassembly is disclosed that includes an electronic component, a modulelid, a heat sink, and a thermal interface material. The module lid formsa heat spreader surrounding the electronic component, and the module lidhas a module lid mating surface. The heat sink has surface features thatprotrude away from a heat sink mating surface, and the thermal interfacematerial is disposed within an interface between the module lid matingsurface and the heat sink mating surface. The surface features protrudeaway from the heat sink mating surface into selected areas of theinterface to limit relative movement of the mating surfaces into theselected areas during thermal cycling of the electronic component inorder to reduce migration of the thermal interface material out of theinterface.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art diagram illustrating that excessive relativemovement of a heat generating component and a heat dissipating componentduring thermal cycling may cause pump-out of thermal interface material.

FIG. 2 is a diagram illustrating an example of a thermal interfacematerial structure in which protruding features are incorporated onto amodule lid mating surface in order to reduce pump-out of thermalinterface material by preventing excessive relative movement duringthermal cycling, according to one embodiment.

FIG. 3 is a diagram illustrating an example of a thermal interfacematerial structure in which protruding features are incorporated onto aheat sink mating surface in order to reduce pump-out of thermalinterface material by preventing excessive relative movement duringthermal cycling, according to one embodiment.

FIG. 4 is a flow diagram depicting a particular embodiment of a processof forming a thermal interface material structure having surfacefeatures incorporated onto a module lid mating surface to preventexcessive relative movement of mating surfaces during thermal cycling inorder to reduce pump-out of thermal interface material.

FIG. 5 is a flow diagram depicting a particular embodiment of a processof forming a thermal interface material structure having surfacefeatures incorporated onto a heat sink mating surface to preventexcessive relative movement of mating surfaces during thermal cycling inorder to reduce pump-out of thermal interface material.

DETAILED DESCRIPTION

The present disclosure describes thermal interface material (TIM)structures that include protruding surface features to reduce TIMmigration (also referred to as “TIM pumping” or “TIM pump-out”). Thethermal interface material structures of the present disclosureincorporate surface features onto a particular mating surface, such thatthe features protrude into selected areas of an interface (including athermal interface material, such as a thermal grease or putty)separating the particular mating surface from another mating surface. Insome cases, the protruding features may be incorporated onto a matingsurface of a heat spreader (also referred to herein as a module lid)that surrounds an electronic component (also referred to herein as alidded module) and distributes heat away from the electronic component.In other cases, the protruding features may be incorporated onto amating surface of a heat sink that overlies the module lid and isseparated from the module lid by the interface (that includes thethermal interface material).

During thermal cycling, a CTE mismatch between the module lid and theheat sink may cause relative motion (in-plane and out-of-plane) betweenthe module lid and the heat sink. By incorporating surface features thatprotrude from a mating surface into selected areas of the interface, thepotential relative movement of the mating surfaces in the selected areasmay be limited. Limiting the relative movement may reduce strain on thethermal interface material in areas of the interface proximate to theprotruding features. Reducing the strain on the thermal interfacematerial may reduce the potential for TIM pump-out and the associatedincrease in thermal resistance due to loss of material from theinterface.

Referring to FIG. 1, a prior art diagram 100 illustrates a heat source102 (e.g., an integrated circuit or other heat-generating component ofan electronic device) that dissipates heat using a heat sink 104 that isjoined to the heat source 102 by a thermal interface material 106, suchas a thermal grease or a thermal putty. The top portion of FIG. 1illustrates that compressing the thermal interface material 106 betweenthe heat source 102 and the heat sink 104 may fill an interface gapbetween a mating surface of the heat source 102 and a mating surface ofthe heat sink 104 in order to form an interface for efficient removal ofheat from the heat source 102 via the heat sink 104.

The heat source 102 and the heat sink 104 may correspond to differentmaterials that have different CTE values. The bottom portion of FIG. 1illustrates that, due to the CTE mismatch between the heat source 102and the heat sink 104, thermal changes associated with thermal cycling(e.g., powering up or powering down of an electronic device) causerelative movement (in-plane and out-of-plane) of the heat source 102 andthe heat sink 104. To illustrate, during thermal cycling, the heatsource 102 may bow upward into a central area of the interface, and theheat sink 104 may bow downward into the central area of the interface,resulting in a significant reduction of interface thickness between theheat source 102 and the heat sink 104 in the central area of theinterface. The resulting strain may cause the thermal interface material106 to migrate away from the central area of the interface over time,identified as TIM pump-out by the dashed lines of FIG. 1. Pump-out ofthe thermal interface material 106 results in increased thermalresistance due to loss of material from the interface.

By contrast, the thermal interface material structures of the presentdisclosure incorporate surface features onto a mating surface of aparticular heat transfer component of an electronic component coolingassembly that includes two heat transfer components (e.g., a heatspreader and a heat sink) separated by an interface that includes athermal interface material (e.g., a thermal grease or putty). The heatspreader surrounds an electronic component and distributes heat awayfrom the electronic component. The heat spreader is also referred toherein as a module lid, and the electronic component within the heatspreader is also referred to herein as a lidded module. In some cases,the surface features may be incorporated onto a mating surface of theheat spreader, as further described with respect to the example depictedFIG. 2. In other cases, the surface features may be incorporated onto amating surface of the heat sink, as further described with respect tothe example depicted FIG. 3.

The surface features protrude from the mating surface of the particularheat transfer component into selected areas of the interface. Asdescribed further herein, the protruding features may limit the relativemovement of the mating surfaces in the selected areas of the interfaceduring thermal cycling due to CTE mismatch. Limiting the relativemovement may reduce strain on the thermal interface material in areas ofthe interface proximate to the protruding features. Reducing the strainon the thermal interface material may reduce the potential for TIMpump-out and the associated increase in thermal resistance due to lossof material from the interface.

Referring to FIG. 2, a diagram 200 illustrates an electronic componentcooling assembly 202 that includes an example of a first TIM structure210 of the present disclosure (identified as “TIM Structure(1)” in FIG.2), according to one embodiment. The electronic component coolingassembly 202 is illustrated in a perspective view on the left side ofFIG. 2, and a selected portion of the electronic component coolingassembly 202 that includes the first TIM structure 210 is illustrated ina cross-sectional view on the right side of FIG. 2. The cross-sectionalview illustrates that the first TIM structure 210 includes a thermalinterface material 212 (e.g., a thermal grease or putty) that forms aninterface between a heat sink 214 and a module lid 216. The perspectiveview illustrates that the module lid 216 corresponds to a heat spreadersurrounding an electronic component 218 that distributes heat generatedby the electronic component 218 during operation. To illustrate, theelectronic component 218 may include a die, a central processing unit(CPU), a graphics processing unit (GPU), or a field programmable gatearray (FPGA), among other alternatives. The first TIM structure 210 ofFIG. 2 represents an example in which protruding features 220 (alsoreferred to herein as “bumps”) are incorporated onto a module lid matingsurface 222 (identified as “Mating Surface(1)” in FIG. 2) in order toreduce or eliminate pump-out of the thermal interface material 212 bypreventing excessive relative movement of the module lid 216 and theheat sink 214 during thermal cycling, such as the excessive relativemovement depicted in the prior art diagram 100 of FIG. 1. Alternativelyor additionally, protruding features may be incorporated onto a heatsink mating surface 224 (identified as “Mating Surface(2)” in FIG. 2),as illustrated and further described herein with respect to FIG. 3.

In the particular embodiment depicted in FIG. 2, the protruding features220 are incorporated onto the module lid 216 and protrude out from themodule lid mating surface 222 into selected areas of the interfacebetween the module lid mating surface 222 and the heat sink matingsurface 224. In a particular embodiment, the protruding features 220 maybe incorporated onto the module lid 216 through a forming process duringmanufacturing of the module lid 216. In another embodiment, channels maybe machined, as indicated by residual lines 250, or otherwiseincorporated into the module lid 216, and the channels may be filledwith a material that is appropriate for the module lid 216 in order toform the protruding features 220. In some cases, the module lid 216 maybe formed from a module lid material, such as a nickel-based material, acopper-based material, an aluminum-based material, or any combinationthereof, among other alternative materials. As an illustrative,non-limiting example, when the module lid 216 is formed from anickel-based material, the channels may be filled with a nickel-basedmaterial that is the same as the nickel-based material of the module lid216 or that is substantially similar to the nickel-based material of themodule lid 216. Alternatively, with respect to the example in which themodule lid 216 is formed from a nickel-based material, the channels maybe filled with other material(s) compatible with the nickel-basedmaterial for efficient transfer of heat away from the module lid 216into the thermal interface material 212.

The bottom portion of FIG. 2 illustrates that the protruding features220 may prevent excessive relative movement of the module lid 216 andthe heat sink 214 during thermal cycling. In the particular embodimentillustrated in FIG. 2, the protruding features 220 are positioned in acentral area of the interface separating the module lid 216 and the heatsink 214. During thermal cycling, the module lid 216 may bow upward intothe central area of the interface, and the heat sink 214 may bowdownward into the central area of the interface. As previously describedherein with respect to the prior art diagram 100 of FIG. 1, this mayresult in a significant reduction of interface thickness in the centralarea. By positioning the protruding features 220 in the central area ofthe interface, the potential reduction of interface thickness in thecentral area is limited by a distance that the protruding features 220extend into the interface from the module lid mating surface 222.

FIG. 2 depicts an illustrative, non-limiting example in which theprotruding features 220 include three protruding features that aredistributed substantially uniformly along the module lid mating surface222 in the central area of the interface. Further, FIG. 2 illustrates anexample in which each of the protruding features 220 has a substantiallysimilar shape (e.g., a bump shape). It will be appreciated that thenumber of protruding features 220, the position/distribution ofprotruding features 220 on the module lid mating surface 222, thesize/shape of each of the protruding features 220, or a combinationthereof, may vary. As an example, in some cases, the protruding features220 may be “strategically” patterned based on characteristics of theindividual components of the electronic component cooling assembly 202,such as characteristics of the heat sink 214 and/or characteristics ofthe module lid 216, among other possible factors. As another example,when the module lid 216 is from a first manufacturer, the module lid 216may tend to bow more to one side than a module lid from a secondmanufacturer. In this case, the protruding features 220 may beincorporated onto the module lid mating surface 222 in a particular“strategic” pattern when the module lid 216 is from the firstmanufacturer, and the protruding features 220 may be incorporated ontothe module lid mating surface 222 in a different “strategic” patternwhen the module lid 216 is from the second manufacturer.

Thus, FIG. 2 illustrates a first example of a thermal interface materialstructure of the present disclosure in which protruding features areincorporated onto a module lid mating surface. In the example of FIG. 2,the features protrude from the module lid mating surface into selectedareas of an interface separating the module lid mating surface from aheat sink mating surface (e.g., into a central area of the interface).The protruding features may limit the relative movement of the matingsurfaces in the selected areas during thermal cycling due to CTEmismatch. Limiting the relative movement may reduce strain on thethermal interface material in areas of the interface proximate to theprotruding features. Reducing the strain on the thermal interfacematerial may reduce the potential for TIM pump-out and the associatedincrease in thermal resistance due to loss of material from theinterface.

Referring to FIG. 3, a diagram 300 illustrates an electronic componentcooling assembly 302 that includes an example of a second TIM structure310 of the present disclosure (identified as “TIM Structure(2)” in FIG.3), according to one embodiment. The electronic component coolingassembly 302 is illustrated in a perspective view on the left side ofFIG. 3, and a selected portion of the electronic component coolingassembly 302 that includes the second TIM structure 310 is illustratedin a cross-sectional view on the right side of FIG. 3. Thecross-sectional view illustrates that the second TIM structure 310includes a thermal interface material 312 (e.g., a thermal grease orputty) that forms an interface between a heat sink 314 and a module lid316. The perspective view illustrates that the module lid 316corresponds to a heat spreader surrounding an electronic component 318that distributes heat generated by the electronic component 318 duringoperation. To illustrate, the electronic component 318 may include adie, a CPU, a GPU, or an FPGA, among other alternatives. The second TIMstructure 310 of FIG. 3 represents an example in which protrudingfeatures 320 (also referred to herein as “bumps”) are incorporated ontoa heat sink mating surface 324 (identified as “Mating Surface(2)” inFIG. 3) in order to reduce or eliminate pump-out of the thermalinterface material 312 by preventing excessive relative movement of themodule lid 316 and the heat sink 314 during thermal cycling, such as theexcessive relative movement depicted in the prior art diagram 100 ofFIG. 1. Alternatively or additionally, protruding features may beincorporated onto a module lid mating surface 322 (identified as “MatingSurface(1)” in FIG. 3), as previously described herein with respect tothe first TIM structure 210 of FIG. 2.

In the particular embodiment depicted in FIG. 3, the protruding features320 are incorporated onto the heat sink 314 and protrude out from theheat sink mating surface 324 into selected areas of the interfacebetween the heat sink mating surface 324 and the module lid matingsurface 322. In a particular embodiment, the protruding features 320 maybe incorporated onto the heat sink 314 through a forming process duringmanufacturing of the heat sink 314. In another embodiment, channels maybe machined or otherwise incorporated into the heat sink 314, and thechannels may be filled with a material that is appropriate for the heatsink 314 in order to form the protruding features 320. In some cases,the heat sink 314 may be formed from a heat sink material, such as analuminum-based material or a copper-based material, among otheralternative materials. As an illustrative, non-limiting example, whenthe heat sink 314 is formed from an aluminum-based material, thechannels may be filled with an aluminum-based material that is the sameas the aluminum-based material of the heat sink 314 or that issubstantially similar to the aluminum-based material of the heat sink314. Alternatively, with respect to the example in which the heat sink314 is formed from an aluminum-based material, the channels may befilled with other material(s) compatible with the aluminum-basedmaterial for efficient transfer of heat to the heat sink 314.

The bottom portion of FIG. 3 illustrates that the protruding features320 may prevent excessive relative movement of the module lid 316 andthe heat sink 314 during power or thermal cycling. In the particularembodiment illustrated in FIG. 3, the protruding features 320 arepositioned in a central area of the interface separating the module lid316 and the heat sink 314. During thermal cycling, the module lid 316may bow upward into the central area of the interface, and the heat sink314 may bow downward into the central area of the interface. Aspreviously described herein with respect to the prior art diagram 100 ofFIG. 1, this may result in a significant reduction of interfacethickness in the central area. By positioning the protruding features320 in the central area of the interface, the potential reduction ofinterface thickness in the central area is limited by a distance thatthe protruding features 320 extend into the interface from the heat sinkmating surface 324.

FIG. 3 depicts an illustrative, non-limiting example in which theprotruding features 320 include three protruding features that aredistributed substantially uniformly along the heat sink mating surface324 in the central area of the interface. Further, FIG. 3 illustrates anexample in which each of the protruding features 320 has a substantiallysimilar shape (e.g., a bump shape). It will be appreciated that thenumber of protruding features 320, the position/distribution ofprotruding features 320 on the heat sink mating surface 314, thesize/shape of each of the protruding features 320, or a combinationthereof, may vary. As an example, in some cases, the protruding features320 may be “strategically” patterned based on characteristics of theindividual components of the electronic component cooling assembly 302,such as characteristics of the heat sink 314 and/or characteristics ofthe module lid 316, among other possible factors.

Thus, FIG. 3 illustrates a second example of a thermal interfacematerial structure of the present disclosure in which protrudingfeatures are incorporated onto a heat sink mating surface. In theexample of FIG. 3, the features protrude from the heat sink matingsurface into selected areas of an interface separating the heat sinkmating surface from the module lid mating surface from a (e.g., into acentral area of the interface). The protruding features may limit therelative movement of the mating surfaces in the selected areas duringthermal cycling due to CTE mismatch. Limiting the relative movement mayreduce strain on the thermal interface material in areas of theinterface proximate to the protruding features. Reducing the strain onthe thermal interface material may reduce the potential for TIM pump-outand the associated increase in thermal resistance due to loss ofmaterial from the interface.

Referring to FIG. 4, a flow diagram illustrates a particular embodimentof a process 400 of forming a thermal interface material structurehaving protruding surface features incorporated onto selected areas of amodule lid mating surface to prevent excessive relative movement ofmating surfaces during thermal cycling in order to reduce pump-out ofthermal interface material. In the particular embodiment depicted inFIG. 4, the process 400 further includes forming an electronic componentcooling assembly that includes the thermal interface material structure.It will be appreciated that the operations shown in FIG. 4 are forillustrative purposes only and that the operations may be performed inalternative orders, at alternative times, by a single entity or bymultiple entities, or a combination thereof. For example, one entity mayincorporate surface features onto selected areas of a module lid, whilethe same entity or a different entity may utilize the module lid (havingthe protruding surface features) to form a heat spreader surrounding anelectronic component. In some cases, another entity may form an assemblyby disposing the thermal interface material (e.g., a thermal grease orputty) on the module lid mating surface (including the protrudingsurface features) and disposing the heat sink mating surface on thethermal interface material, while the same entity or a different entitymay compress the assembly to form the electronic component coolingassembly that includes the thermal interface material structure.

The process 400 includes incorporating surface features onto selectedareas of a first mating surface associated with a module lid, at 402.The surface features protrude from the first mating surface. Forexample, referring to the first TIM structure 210 depicted in FIG. 2,the module lid 216 may have the protruding features 220 incorporatedonto the module lid mating surface 222. In some cases, the protrudingfeatures 220 may be formed during formation of the module lid 216. Inother cases, while not shown in the example of FIG. 2, after formationof the module lid 216 (having the module lid mating surface 222),channels may be machined into the module lid mating surface 222, and thechannels may be filled with a material that is appropriate for theparticular module lid material (e.g., a nickel-based material, in somecases)

In the particular embodiment depicted in FIG. 4, the process 400includes utilizing the module lid having the protruding surface featuresincorporated onto the first mating surface to form a heat spreadersurrounding an electronic component, at 404. Referring to FIG. 2, afterincorporating the protruding features 220 onto the module lid matingsurface 222, the module lid 216 (including the protruding features 220)may be used to form a heat spreader surrounding the electronic component218. In other cases, the protruding features 220 may be formed on themodule lid mating surface 222 after the module lid 216 has been utilizedto form a heat spreader to surround the electronic component 218.

The process 400 also includes forming an assembly that includes athermal interface material disposed between the module lid matingsurface (having the protruding surface features) and a heat sink matingsurface, at 406. The process further includes compressing the assemblyto form an electronic component cooling assembly having a thermalinterface material structure that includes the thermal interfacematerial disposed within an interface defined by the module lid matingsurface and the heat sink mating surface, at 408.

For example, referring to FIG. 2, the electronic component coolingassembly 202 may be formed by compressing an assembly that includes thethermal interface material 212 disposed between the module lid matingsurface 222 (having the protruding features 220) and the heat sinkmating surface 224. The right side of FIG. 2 illustrates that, aftercompression, the electronic component cooling assembly 202 includes thefirst TIM structure 210 in which the thermal interface material 212 isdisposed within an interface defined by the module lid mating surface222 and the heat sink mating surface 222.

The bottom portion of FIG. 2 illustrates that the protruding features220 may prevent excessive relative movement of the module lid 216 andthe heat sink 214 during thermal cycling. In the particular embodimentillustrated in FIG. 2, the protruding features 220 are positioned in acentral area of the interface separating the module lid 216 and the heatsink 214. During thermal cycling, the module lid 216 may bow upward intothe central area of the interface, and the heat sink 214 may bowdownward into the central area of the interface. As previously describedherein with respect to the prior art diagram 100 of FIG. 1, this mayresult in a significant reduction of interface thickness in the centralarea. By positioning the protruding features 220 in the central area ofthe interface, the potential reduction of interface thickness in thecentral area is limited by a distance that the protruding features 220extend into the interface from the module lid mating surface 222.

Thus, FIG. 4 illustrates an example of a process of forming a thermalinterface material structure having protruding surface featuresincorporated onto selected areas of a module lid mating surface toprevent excessive relative movement of mating surfaces during thermalcycling in order to reduce pump-out of thermal interface material.

Referring to FIG. 5, a flow diagram illustrates a particular embodimentof a process 500 of forming a thermal interface material structurehaving protruding surface features incorporated onto selected areas of aheat sink mating surface to prevent excessive relative movement ofmating surfaces during thermal cycling in order to reduce pump-out ofthermal interface material. In the particular embodiment depicted inFIG. 5, the process 500 further includes forming an electronic componentcooling assembly that includes the thermal interface material structure.It will be appreciated that the operations shown in FIG. 5 are forillustrative purposes only and that the operations may be performed inalternative orders, at alternative times, by a single entity or bymultiple entities, or a combination thereof. For example, one entity mayutilize a module lid to form a heat spreader surrounding an electroniccomponent, while another entity may incorporate surface features ontoselected areas of the heat sink mating surface. In some cases, anotherentity may form an assembly by disposing the thermal interface material(e.g., a thermal grease or putty) on the module lid mating surface anddisposing the heat sink mating surface (including the protruding surfacefeatures) on the thermal interface material, while the same entity of adifferent entity may compress the assembly to form the electroniccomponent cooling assembly that includes the thermal interface materialstructure.

The process 500 includes disposing a thermal interface material on amating surface of a module lid, at 502. The module lid forms a heatspreader surrounding an electronic component. For example, referring toFIG. 3, the module lid 316 may form a heat spreader surrounding theelectronic component 318, and the thermal interface material 312 may bedisposed on the module lid mating surface 322.

The process 500 includes incorporating surface features onto selectedareas of a heat sink mating surface, at 504. The surface featuresprotrude from the heat sink mating surface. For example, referring tothe second TIM structure 310 depicted in FIG. 2, the heat sink 314 mayhave the protruding features 320 incorporated onto the heat sink matingsurface 324. In some cases, the protruding features 320 may be formedduring formation of the heat sink 314. In other cases, while not shownin the example of FIG. 3, after formation of the heat sink (having theheat sink mating surface 324), channels may be machined into the heatsink mating surface 324, and the channels may be filled with a materialthat is appropriate for the particular heat sink material (e.g., analuminum-based material, in some cases).

The process 500 also includes forming an assembly that includes thethermal interface material disposed between the module lid matingsurface and the heat sink mating surface (having the protruding surfacefeatures), at 506. The process further includes compressing the assemblyto form an electronic component cooling assembly having a thermalinterface material structure that includes the thermal interfacematerial disposed within an interface defined by the module lid matingsurface and the heat sink mating surface, at 508.

For example, referring to FIG. 3, the electronic component coolingassembly 302 may be formed by compressing an assembly that includes thethermal interface material 312 disposed between the module lid matingsurface 322 the heat sink mating surface 324 (having the protrudingfeatures 320). The right side of FIG. 3 illustrates that, aftercompression, the electronic component cooling assembly 302 includes thesecond TIM structure 310 in which the thermal interface material 312 isdisposed within an interface defined by the module lid mating surface322 and the heat sink mating surface 324.

The bottom portion of FIG. 3 illustrates that the protruding features320 may prevent excessive relative movement of the module lid 316 andthe heat sink 314 during thermal cycling. In the particular embodimentillustrated in FIG. 3, the protruding features 320 are positioned in acentral area of the interface separating the module lid 316 and the heatsink 314. During thermal cycling, the module lid 316 may bow upward intothe central area of the interface, and the heat sink 314 may bowdownward into the central area of the interface. As previously describedherein with respect to the prior art diagram 100 of FIG. 1, this mayresult in a significant reduction of interface thickness in the centralarea. By positioning the protruding features 320 in the central area ofthe interface, the potential reduction of interface thickness in thecentral area is limited by a distance that the protruding features 320extend into the interface from the heat sink mating surface 324.

Thus, FIG. 5 illustrates an example of a process of forming a thermalinterface material structure having protruding surface featuresincorporated onto selected areas of a heat sink mating surface toprevent excessive relative movement of mating surfaces during thermalcycling in order to reduce pump-out of thermal interface material.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

What is claimed is:
 1. An electronic component cooling assemblycomprising: an electronic component; a module lid to form a heatspreader surrounding the electronic component, the module lid havingmachined channels, the machined channels having a module lid materialfill, the module lid material fill including at least a nickel-basedmaterial and generating surface features of the module lid that protrudeaway from a module lid mating surface; a heat sink having a heat sinkmating surface; and a thermal interface material that is a thermalgrease and that is disposed within an interface between the module lidmating surface and the heat sink mating surface, wherein the surfacefeatures protrude away from the module lid mating surface into selectedareas of the interface and make contact with the heat sink matingsurface.
 2. The electronic component cooling assembly of claim 1,wherein the module lid and the surface features include the nickel-basedmaterial, a copper-based material, an aluminum-based material, or anycombination thereof.
 3. The electronic component cooling assembly ofclaim 1, wherein the module lid is formed from a first material, andwherein the surface features are formed from a second material that iscompatible with the first material for efficient transfer of heat fromthe module lid into the thermal interface material during operation ofthe electronic component.
 4. The electronic component cooling assemblyof claim 1, wherein the electronic component includes a die, a centralprocessing unit, a graphics processing unit, or a field programmablegate array.
 5. The electronic component cooling assembly of claim 1,wherein the surface features protrude away from the module lid matingsurface into the selected areas of the interface to limit relativemovement of the module lid mating surface, and wherein the surfacefeatures protrude away from the module lid mating surface making contactwith the heat sink mating surface into the selected areas during thermalcycling of the electronic component in order to reduce migration of thethermal interface material out of the interface.